1. Field of the Invention
The present invention relates to a lower roll apparatus for a single facer.
2. Description of the Prior Art
A lower roll apparatus for a conventional single facer will first be described with reference to FIGS. 1 to 5.
A lower roll 5 which is shown in FIG. 1 has its outer peripheral surface provided with corrugated grooves 5a which extend axially thereof and circumferential grooves 5b which extend circumferentially thereof, as shown in FIG. 2. The roll cell of the lower roll 5 is formed with horizontal bores 5d which extend axially thereof. The horizontal bores 5d are respectively communicated with the valley portions of the circumferential grooves 5b through respective suction bores 5e. On the other hand, suction boxes 12 are respectively provided in close proximity to the right and left ends of the lower roll 5. The suction boxes 12 and the corresponding outer end surfaces of the lower roll 5 are hermetically connected through respective disk plates 11. Both shaft portions 5c of the lower roll 5 are rotatably supported by a frame (not shown) in such a manner that both the outer end surfaces of the lower roll 5 are in slide contact with the respective side surfaces of the disk plates (see FIGS. 3 and 4).
FIG. 5 schematically shows the process of manufacturing a single-faced corrugated sheet in a conventional single facer. In the Figure, the reference numeral 5 denotes a lower roll having the above-described structure. An upper roll 4 has its outer peripheral surface provided with corrugated grooves 4a similar to those formed on the outer peripheral surface of the lower roll 5. The reference numeral 6 represents a pressure roll, 7 a gluing roll, 8 a glue reservoir, 9 glue, and 10 a scraper.
A core paper sheet 1 is fed in the direction of the arrow and is shaped into a corrugated sheet 1a while passing through the engagement area between the upper and lower rolls 4 and 5, and the glue 9 is attached to the crests of the corrugations of the sheet 1a by the gluing roll 7 as shown by the reference numeral 9a. On the other hand, a liner 2 which is fed in the direction of the arrow is press-bonded to the core paper sheet 1a while passing through the engagement area between the pressure roll 6 and the lower roll 5 to form a single-faced corrugated sheet 3, which is fed to a subsequent step.
During such a process, the core paper sheet 1a is held to the surface of the lower roll 5 by means of suction over a range corresponding to an angle .theta. shown in FIG. 3. However, when such a suction operation is carried out continuously, the suction bores 5e gradually become clogged with paper powder and the glue 9, causing the suction effected to be gradually decreased. Finally, the core paper sheet 1a is undesirably fed to the gluing roll 7 in a state wherein it is not completely suction-attached to the lower roll 5, resulting disadvantageously in a single-faced sheet which is incompletely corrugated. For this reason, it has been inconveniently necessary in order to prevent this clogging phenomenon to suspend operation of the machine and to clean the bores 5d and 5e manually. Further, a large number of defective sheets may disadvantageously be produced due to this clogging phenomenon.
To prevent clogging of the suction bores so as to maintain a required level of productivity, it is general practice to periodically clean the suction bores manually. However, since there are a large number of suction bores, much time is disadvantageously required for cleaning.